Genetic canalization of nutrient resorption in the widespread grass <i>Phragmites australis</i> under salt stress

The widespread grass Phragmites australis demonstrates a genetic mechanism known as canalization, which maintains nutrient resorption efficiency (NuRE) despite exposure to salinity stress. This study, involving 110 genotypes of the cosmopolitan grass, revealed that salinity treatment led to significant declines in above-ground biomass and sodium accumulation. Additionally, 484 metabolites exhibited differential accumulation, primarily associated with osmotic and oxidative stress.

Despite these environmental stresses, NuRE remained largely unaffected by the presence of salt. Instead, the study discovered that NuRE was strongly correlated with the phylogeographic lineage, ecotype, and latitude of origin of the plant. This suggests a form of evolutionary canalization, where intrinsic genetic differences rather than short-term acclimation mechanisms drive the response to salinity stress.

The research also highlighted element-specific regulatory patterns. While phosphorus resorption showed concentration-dependent control irrespective of stress, nitrogen resorption was disrupted under salinity conditions, and potassium resorption did not demonstrate such dependence. These findings underscore that intraspecific variation in nutrient resorption is predominantly shaped by historical adaptation and geographic context, rather than by plasticity to salinity stress.

The implications of this genetic canalization are significant for predictions of nutrient cycling under global change. Specifically, it suggests that considerations of the phylogeographic composition of plant populations must be integrated into models forecasting nutrient dynamics in the face of increasing salinity levels due to climate change.